In the desalting method of fuel oil, excepting a specific method, it would be conventional and known to separate water and sludge from the oil by making use of centrifugal force or static electricity, but the mixture of salt-containing water and sludge separated out of the oil have been discarded, and moreover there is no treating device suitable for the sludge comprising water, salts, heavy oil sludge and the like.
In the operation of desalting device, it is necessary to use clean washing water in an amount of about 1% based on the fuel oil, which water has never been reused in general. Accordingly, it was impossible to set up a plant of this kind in such a region as a desert region or the like where water is hardly available.
Further, as the separated heavy sludge containing both salts and water, there is no suitable treating device, and therefore any effective treating method has not yet been established.
A main object of the desalting is to eliminate sodium and potassium salts contained in fuel oil, which salts are mainly composed of sodium chloride and potassium chloride formed by the bond with chlorine and exist in the fuel oil either in the form of solution in a small amount of water contained therein or in the form of fine solid. It is known that these salts are soluble in water and therefore the elimination of sodium and potassium salts can be accomplished by washing the fuel oil with water to transfer the sodium and potassium salts into washing water and then separating the water from the fuel oil.
Referring to FIG. 1, a desalting apparatus of prior art is explained. Fuel oil 5 stored in a fuel oil tank 3 is led through a fuel oil pump 4 to a sludge separator 1, in which water and sludge contained in small amount in the fuel oil are separated as a heavy portion 6 from a desludge oil 7, taken out and then led to a waste water-treating equipment. Into the sludge-removed oil 7 feed from the heavy portion 6 is poured an emulsion breaker 10 from an emulsion breaker tank 8 through a pump 9, thereafter newly deionized clean water 13 is incorporated thereinto from a clean water tank 11 through a pump 12, and then the mixture is thoroughly mixed in a mixer 14 so as to dissolve salts contained in the sludge-removed oil 7 in water. The mixed liquid is led to a desaltor 2, in which a salt-containing water 15 is separated as a heavy portion from the oil, and then led to a waste water-treating equipment. The oil freed from the salt-containing water 5 contains only a very small quantity of salts and can be dealt with as a desalted fuel oil 16. In this manner, however, newly deionized clean water must be used and moreover the treatment of the separated heavy portion is left unsolved.